A. It is named after Ernst Mach, a scientist who studied supersonic missiles in the late 19th century.

Q. What is thunder?

A. Thunder is the 'push' of sound waves from lightning.

Q. Why do we hear thunder some time after we see the lightning?

A. The speed of light is much faster than the speed of sound, so we see the lightning long before we see hear the thunder.

Q. Why is your voice distorted if you speak into a moving desk fan set at a distance close to you?

A. Sound is vibrations of air. Since the air is moving around a fan, this will distort the waves of sound, so your voice sounds strange.

Q. Why did American Indians put their ears to the ground to hear if the cowboys were coming?

A. Sound travels faster through solids than through the air, so the Indians could hear the cowboys even before they could see them.

Q. What is a whip crack?

A. The tip of whip travels faster than the speed of sound, creating a sonic boom.

Q. How many telephones were invented by Alexander Graham Bell?

A. Two (Ha!Ha!)

Q. Why do cars coming towards you sound different to cars travelling away from you?

A. This is called the Doppler Effect. As a car comes towards you, the sound waves also come towards you and are squashed up so you hear a higher frequency. As the car moves away from you so do the sound waves, they become more widely spaced apart. You hear a lower frequency.